AMC8 2002 Problem 10

Juan organizes the stamps in his collection by country and by the decade in which they were issued. The prices he paid for them at a stamp shop were: Brazil and France, 6 \phi each, Peru 4 \phi each, and

Number of Stamps by Decade

\begin{array}{|c|c|c|c|c|} \hline \textbf{Country} & \textbf{'50s} & \textbf{'60s} & \textbf{'70s} & \textbf{'80s} \\ \hline \text{Brazil} & 4 & 7 & 12 & 8 \\ \hline \text{France} & 8 & 4 & 12 & 15 \\ \hline \text{Peru} & 6 & 4 & 6 & 10 \\ \hline \text{Spain} & 3 & 9 & 13 & 9 \\ \hline \end{array}

Juan’s Stamp Collection Spain 5 \$ each. (Brazil and Peru are South American countries and France and Spain are in Europe.) The average price of his '70s stamps is closest to

Answer Choices
A. 3.5 ф
B. 4 \notin
C. 4.5 \phi
D. 5 申
E. 5.5 申