prelab question 10 and 11 please help me solve

10.) Quantities which are directly measurable in this lab are the accelerating voltage AV, radius of the electron's path r, and the magnetic field B. Combine your results from steps 6 and 9 to write a formula which relates the radius of the electron's path r to other measurable quantities, and the ratio e/m. You should be able to write this equation in the form C T= B (1) where C is a constant. Determine an expression for the constant C' in terms of mea- sureable quantities and the charge to mass ratio e/m. 11.) In this lab you can vary B and measure r. Explain how you could plot your data in such a way that you could determine e/m from the slope of a graph