A proton initially has v→ = (−2.00)i^ + (5.40)j^ + (7.80)k^ and then 4.30 s later has v→ = (−17.0)i^ + (5.40)j^ + (11.0)k^ (in meters per second). (a) For that 4.30 s, what is the proton's average acceleration a→ avg in unit vector notation, (b) in magnitude, and (c) the angle between a→ avg and the positive direction of the x axis? (a) Number i^ k^ Units (b) Number Units (c) Number Units