Point Charges $+ 4.00 \mu \mathrm { C }$ And $+ 2.00 \mu \mathrm { C }$

Point charges $+ 4.00 \mu \mathrm { C }$ and $+ 2.00 \mu \mathrm { C }$ are placed at the opposite corners of a rectangle as shown in the figure. What is the potential at point B due to these charges? $\left( k = 1 / 4 \pi \varepsilon _ { 0 } = 8.99 \times 10 ^ { 9 } \mathrm {~N} \right.$ . $\mathrm { m } ^ { 2 } / \mathrm { C } ^ { 2 }$ )

A) $89.9 \mathrm { kV }$
B) $8.99 \mathrm { kV }$
C) $11.2 \mathrm { kV }$
D) $899 \mathrm { kV }$
E) $112 \mathrm { kV }$