A cube with its sides numbered \(1— 6\) is rolled twice, first landing on \(a\) and then landing on \(b.\) If any roll

A cube with its sides numbered \(1— 6\) is rolled twice, first landing on \(a\) and then landing on \(b.\) If any roll of the cube yields an equal chance of landing on any of the numbers \(1 — 6,\) what is the probability that \(a + b\) is prime?

A) \(0\)

B) \(\dfrac1{12}\)

C) \(\dfrac5{12}\)

D) \(\dfrac7{18}\)

E) \(\dfrac49\)

Answer: C

Source: Manhattan GMAT