Answer:
645 feet.
Step-by-step explanation:
I. Given plus is rise up and minus is goes down, when the submarine is underwater so
{submarine} = -645
{rise up} = +100 -645
= -545
{go down} = -100 - 545
= -645 or 645 feet underwater
That makes -645 is the interger represents the charge of submarine position.
Hope that help :)