EXHIBIT 10.13(b)AMENDMENT NO. 1 TO RETIREMENT BENEFIT AGREEMENT          THIS AMENDMENT NO. 1 TO RETIREMENT BENEFIT AGREEMENT (this “Amendment”) by and between MylanLaboratories Inc., a Pennsylvania corporation (the “Company”), and Stuart A. Williams (the“Executive”), is made as of April 3, 2006.          WHEREAS, the Company and the Executive are parties to that certain Retirement BenefitAgreement dated as of December 31, 2004 (the “Agreement”);          WHEREAS, the Company and the Executive wish to amend the Agreement, effective as of April 1,2006, as set forth below;          NOW, THEREFORE, for good and valuable consideration, the receipt and adequacy of which arehereby acknowledged, the parties hereto, intending to be legally bound, agree as follows: 1. Section I(h) of the Agreement is hereby deleted and replaced in its entirety to readas follows:““NPV” shall mean the sum of the present value at any given time of the monthly benefits to bepaid, using a discount rate equal to the long-term applicable federal rate then in effect(determined under Section 1274(d) of the Code), compounded semiannually. For purposes ofdetermining NPV of Executive’s Retirement Benefit (or Partial Retirement Benefit) whereExecutive Retires prior to attaining age 55, it shall be assumed that Executive’s RetirementBenefit (or Partial Retirement Benefit) would have commenced at the date on which Executivewould have attained age 55 and the NPV of such Retirement Benefit (or Partial RetirementBenefit) shall equal the present value of such Benefit at age 55 discounted back to theExecutive’s actual age at Retirement using the rate prescribed in the preceding sentence.Executive’s age for purposes of this Agreement shall be Executive’s age at his nearestbirthday.” 2. Section 2.1 is hereby deleted and replaced in its entirety to read as follows:“Upon his Retirement from the Company after completion of at least ten or more continuous yearsof service (the “Full Vesting Date”), Executive shall receive the NPV of an annual retirementbenefit equal to one hundred and fifty thousand dollars ($150,000) for a period of fifteen (15)years (the “Retirement Benefit”), paid in accordance with Section 2.6 of this Agreement;provided, however, that if Executive Retires on or after the completion of at least five yearsof continuous service and prior to the Full Vesting Date, Executive shall be entitled toreceive the NPV of a portion of the Retirement Benefit determined as follows (“PartialRetirement Benefit”) and paid in accordance with Section 2.6 of this Agreement:     (a) If such termination occurs on or after five years of continuous service but prior tosix years of continuous service, 50% of the Retirement Benefit;
 

 
     (b) If such termination occurs on or after six years of continuous service but prior toseven years of continuous service, 60% of the Retirement Benefit;     (c) If such termination occurs on or after seven years of continuous service but prior toeight years of continuous service, 70% of the Retirement Benefit;     (d) If such termination occurs on or eight years of continuous service but prior to nineyears of continuous service, 80% of the Retirement Benefit;     (e) If such termination occurs on or after nine years of continuous service but prior tothe Full Vesting Date, 90% of the Retirement Benefit;In computing years of service for purposes of this Section 2.1, a period of at least six fullmonths of employment and less than one year shall be deemed to be one full year, and a periodof less than six full months shall be deemed to be zero years. If Executive Retires inconnection with a Termination without Cause or a Termination for Good Reason (pursuant to theExecutive Employment Agreement entered into by and between the Company and Executive effectiveas of July 1, 2004, as amended April 3, 2006 (the “Employment Agreement”)) (other than in theevent the Executive’s employment is terminated (i) by reason of disability or (ii) by reason ofthe non-extension or non-renewal of the Employment Agreement), then Executive shall be creditedwith additional years of service for purposes of vesting under this Section 2.1 equal to therelevant multiplier applied for purposes of computing such severance benefits.” 3. Section 2.6 of the Agreement shall be deleted and replaced in its entirety with thefollowing:“Within ten (10) days following Executive’s Retirement, Executive’s Retirement Benefit orPartial Retirement Benefit, as the case may be, shall be paid to Executive in a lump sumpayment equal to the NPV of the Retirement Benefit or Partial Retirement Benefit, as the casemay be. Notwithstanding the above, if required by Section 409A of the Code to avoid theimposition of additional taxes, such payment shall be made on the date that is six (6) monthsfollowing the date of such Retirement.” 4. This Amendment shall be governed by, interpreted under and construed in accordancewith the laws of the Commonwealth of Pennsylvania.  5. This Amendment may be executed in counterparts, each of which shall be an originaland all of which shall constitute the same document.  6. Except as modified by this Amendment, the Agreement is hereby confirmed in allrespects.
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          IN WITNESS WHEREOF, this Amendment has been duly executed and delivered as of the date and theyear first written above.         MYLAN LABORATORIES INC.         By: /s/ Robert J. Coury          Name: Robert J. Coury  Title: Vice Chairman and CEO         EXECUTIVE           /s/ Stuart A. Williams      Stuart A. Williams 
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