Im having trouble understanding this practice problem of weighted average.

You planned and implemented a fundraising event for your non-profit organization. Donors had the option to donate $10, $25, $50, or $100 to enter the event. The table below includes the number of people who donated each amount. Calculate the weighted average donation. Donation Number of Amount donors $10 15 $25 55 $50 20 $100 10 What does the standard deviation tell you about your data