During the last four years, a large truck company purchased diesel at rates of $1.2, $1.3, $1.8 and $2.1 per gallon. What was the mean cost of diesel over the four-year period if the company spends the same amount of dollars on diesel each year?	Choose one:
A) $2.5 B) $2.55 C) $1.52 D) $3.25 E) $3.0
finding the Harmonic mean here.   HM = 4/(1/12 + 1/13 + 1/18 + 1/21) = 15.18   $1.52
<result>C</result>
During the last four years, a large truck company purchased diesel at rates of $1.2, $1.3, $1.8 and $2.1 per gallon. What was the mean cost of diesel over the four-year period if the company spends the same amount of dollars on diesel each year?