A proton enters a sequence of two parallel-plate regions. First, it passes through a region where the electric potential drops by 2.00 kV, and immediately afterward it enters a region where the potential rises by 1.50 kV. If the proton’s speed just before the first region is 4.0×105m⋅s−1, what is its speed after emerging from the second region? (Proton mass mp=1.67×10−27kg, charge magnitude e=1.6×10−19C.)
a) 2.5×105m⋅s−1
b) 3.1×105m⋅s−1
c) 5.1×105m⋅s−1
d) 7.3×105m⋅s−1