Answer:
a) 0.4286 = 42.86% probability that the low bid on the next intrastate shipping contract is below $24,000.
b) 0.1429 = 14.29% probability that the low bid on the next intrastate shipping contract is in excess of $27,000.
Explanation:
An uniform probability is a case of probability in which each outcome is equally as likely.
For this situation, we have a lower limit of the distribution that we call a and an upper limit that we call b.
The probability that we find a value X lower than x or equal is given by the following formula.

The probability that we find a value X greater than x is given by the following formula.

Uniformly distributed between 21 and 28
This means that

a. Find the probability that the low bid on the next intrastate shipping contract is below $24,000.

0.4286 = 42.86% probability that the low bid on the next intrastate shipping contract is below $24,000.
b. Find the probability that the low bid on the next intrastate shipping contract is in excess of $27,000.

0.1429 = 14.29% probability that the low bid on the next intrastate shipping contract is in excess of $27,000.