A newly opened juice shop offers three types of beverages: juice, milk tea, and coffee. The sales volume (in cups) and total revenue (in yuan) for each type of beverage over the first 3 days are shown in the table below. For example, on the first day, the sales of juice, milk tea, and coffee were 60 cups, 80 cups, and 50 cups respectively, with total revenue of 12,900 yuan.

It is known that the price of each type of beverage is the same every day. Then the price per cup of coffee is

\begin{center}
\begin{tabular}{|l|l|l|l|l|}
\hline
 & Juice (cups) & Milk Tea (cups) & Coffee (cups) & Total Revenue (yuan) \\
\hline
Day 1 & 60 & 80 & 50 & 12900 \\
\hline
Day 2 & 30 & 40 & 30 & 6850 \\
\hline
Day 3 & 50 & 70 & 40 & 10800 \\
\hline
\end{tabular}
\end{center}