A charge is placed at the origin.

a$.$ If the potential at $3\mathrm{.}0$ m from the charge is $380$V$,$ what is the value of the charge?

b$.$ If the potential at $3\mathrm{.}0$ m from the charge is $-380$V$,$ what is the value of the charge?

c$.$ What charge would produce a voltage of $-760$V at $3\mathrm{.}0$m from the charge?