Sum of Squares

How many $P$ points that belong to the y-axis exist such that the distance from $P$ to $A\left( -1,-3 \right)$ squared plus, the distance from $P$ to $B\left( -4,-2 \right)$ squared is equal to 5?

${ \left( { d }_{ PA } \right) }^{ 2 }+{ \left( { d }_{ PB } \right) }^{ 2 }\quad =\quad 5$