A submarine experiences a pressure of 5.05 × 10
6
Pa at a depth of d
1
in a sea. When it goes further to a depth
of d
2
, it experiences a pressure of 8.08 × 10
6
Pa. Then d
2
–d
1
is approximately (density of water = 10
3
kg/m
3
and acceleration due to gravity = 10 ms
–2
) :