If you deposit $3,000 in a savings account that earns simple interest at a rate of 2.5% a year, how much interest would you have after 4 years?

Can someone answer these problems for me

On a string instrument, the length of a string varies inversely as the frequency of its vibrations. an 11-inch string has a frequency of 400 cylces per second. find the frequency of a 10-icnch string.

Find the volume of the solid obtained by rotating the region enclosed by the curves y=1x and y=7^-x about the x-axis. (use symbolic notation and fractions where needed.) volume =