During the last four years, a large truck company purchased diesel at rates of $1.2, $1.4, $1.5 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? Select the correct option:
A) $2.5	B) $2.55	C) $1.49	D) $3.25	E) $3.0
finding the Harmonic mean here.   HM = 4/(1/12 + 1/14 + 1/15 + 1/21) = 14.87   $1.49
<result>C</result>
During the last four years, a large truck company purchased diesel at rates of $1.2, $1.4, $1.5 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?