Martina purchased a prepaid phone card for $20. Long distance calls cost 21 cents a minute using this card. Martina used her card only once to make a long distance call. If the remaining credit on her card is $11.39, how many minutes did her call last?

answer:   35 % is the probability of a late departure or an early arrival.

step-by-step explanation:

let l represents the late departure and e represents the early departure.

then, according to the question,

p(l) = 12 %,   p(e) = 27 % and = 4 %

and, we have to find out,

but, we know that,

which is the required equation that will use to find the probability of a late departure or an early departure.

therefore,   the probability of a late departure or an early arrival =   35 %