Light glows for every 18 seconds . How many times did it between 1:57:58 and 3:20:47 am  Choose the most appropriate option:  A) 281  B) 277  C) 283  D) 384  E) 385

Rationale: "the diff in sec between 1 : 57 : 58 and 3 : 20 : 47 is 4969 sec , 4969 / 18 = 276 . so total 277 times light ll glow answer : b"
Answer: B