Answer
a) It cannot be determined.
b) $V=5I$
c) It cannot be determined.
d) $V = 10I + 4$
e) $V = 5I -7.5$
Work Step by Step
a) This value cannot be determined, for current is dependent on the resistance of the attached circuit, which is not given.
b) We know the following equation: $V=IR$. Using the given value for the resistance of $5 \Omega$, it follows: $\fbox{V=5I}$.
c) The voltage will depend on the elements attached to the source, so like part a, we cannot find the relationship.
d) We use Kirchhoff's Voltage Law, which states that the voltage around a closed loop in a circuit is 0, as well as the value of the resistance to find: $\fbox{V = 10I + 4}$
e) We use Kirchhoff's Voltage Law, which states that the voltage around a closed loop in a circuit is 0, as well as the value of the resistance to find: $\fbox{V = 5I -7.5}$