Question $3-7$ points

A proton moves at ${10}^6\frac{m}{s}$ rightwards when it encounters a region where there is uniform magnetic field of magnitude ${10}^{-3}T$ confined to a rectangular region and directed perpendicular to the page. The proton undergoes a semicircular trajectory and exits the field.

a$)$ Determine the length of the semicircular path $(C=2r).$

b$)$ What is the direction of the magnetic field? Explain.

c$)$ Suppose instead of a proton, an electron entered the field moving the same direction $($rightwards$)$ and at the same speed as the proton. Identify two ways in which the electron's trajectory would be different and explain