Evaluate (exp(-4t)u(t))*u(t), u(t) being the heaviside function.

A)
(1-exp(4t)) u(t)/a
B)
(1-exp(-4t)) u(t)/a
C)
(1-exp(=4t)) u(t)/a
D)
(1+exp(-4t)) u(t)/a

Correct Answer : Option (B) :   (1-exp(-4t)) u(t)/a


Explanation : Use the convolution formula.