Answer
$25$ million phones
Work Step by Step
We expext a shortage, because ${{\$}} 105$ is below the equilibrium price (which we found in part (a)).
When p=105,
Demand:
$\quad\left[\begin{array}{l}
q=-105+156\\
q=51
\end{array}\right]\quad $
Supply:
$\left[\begin{array}{l}
q=4(105)-394\\
q=26
\end{array}\right]$
The demand is $51-26=25$ million phones greater than the supply. That is, there is a shortage of $25$ million phones.
