Answer
The diameter of the hole at $23^{\circ}$ is $4.511 mm$
Work Step by Step
The value of $d_{^{\circ}}$ is 4.5 mm because when the rivet is cooled, the diameter of the hole is equal to the diameter of the rivet.
$d=d_{^{\circ}}$$(1+α\timesδT)$
$d = 4.5 mm (1+2.4\times10^{-5}\times^{^{\circ}}(C)^{-1}\times(23^{^{\circ}}C-(-78^{^{\circ}}C)$
$d=4.511 mm$
