Let T be a continuous random variable representing the amount of time (in minutes) a postal clerk spends with her customer. The time is known to have an exponential distribution with the average amount of time equal to = 4 minutes i. e. the exponential decay parameter is m = 1/μ = 1/4. The corresponding probability density function is described by DeteThe probability distribution function of the clerk's service per customer time, F(t) The probability distribution function of the clerk's service per customer time, F(t) , is:

a) F(t) = (1/4) * e⁻ᵗ/⁴
b) F(t) = (1/4) * eᵗ/⁴
c) F(t) = (1/4) * e⁻⁴/ᵗ
d) F(t) = (1/4) * e⁴/ᵗ