Light glows for every 20 seconds . How many max. times did it glow between 1:57:58 and 3:20:47 am. Choose the correct choice from the following answers:
A) 380 times  B) 381 times  C) 382 times  D) 248 times  E) 482 times

Rationale: "time difference is 1 hr , 22 min , 49 sec = 4969 sec . so , light glows floor ( 4969 / 20 ) = 248 times . answer : d"
Answer: D