A Keplerian telescope with magnification = 15 was submerged into water which filled up the inside of

Question:

A Keplerian telescope with magnification Γ = 15 was submerged into water which filled up the inside of the telescope. To make the system work as a telescope again within the former dimensions, the objective was replaced .What has the magnification of the telescope become equal to? The refractive index of the glass of which the ocular is made is equal to n = 1.50.