Given the following cost and activity observations for Bounty Company's utilities, use the high-low method to determine Bounty's variable utilities cost per machine hour. Round your answer to the nearest cent.
Cost Machine Hours
March $3,018 15,239
April 2,628 9,504
May 2,857 11,534
June 3,730 18,045
a. $0.86
b. $1.42
c. $0.13
d. $0.90