Light glows for every 21 seconds . How many max. times did it glow between 1:57:58 and 3:20:47 am.
Choose the correct option:
A) 380 times
B) 236 times
C) 382 times
D) 392 times
E) 482 times

Rationale: "time difference is 1 hr , 22 min , 49 sec = 4969 sec . so , light glows floor ( 4969 / 21 ) = 236 times . answer : b"
Answer: B