Calculate the integral ∫ _0^5 (14f(x)+(1/3)g(x))dx given that ∫ _0^5 f(x)dx=12 and ∫ _0^5 g(x)dx=6. Provide your answer as a whole or exact number. Which of the following options is correct?

A) ∫ _0^5 (14f(x)+(1/3)g(x))dx=18
B) ∫ _0^5 (14f(x)+(1/3)g(x))dx=20
C) ∫ _0^5 (14f(x)+(1/3)g(x))dx=24
D) ∫ _0^5 (14f(x)+(1/3)g(x))dx=30'