How many even integers n, such that 20<=n<=250 are of the form 3k+4, where k is any natural number?  Choose the correct choice from the following answers.
A) 33  B) 36  C) 39  D) 42  E) 45

Rationale: "the first number is 22 = 16 + 6 ( 1 ) . we can continue adding 6 to make a list : 22 , 28 , 34 , . . . the last number is 250 = 16 + 6 ( 39 ) there are 39 numbers in the list . the answer is c ."
Answer: C