Naveen has 25,000 rupees,in which he gave 10,000 rupees to friend (A) at 10% per annum for two year,then

S.I of 10,000 rupees in two years = (10000×2×10) ÷ 100 = 2000 rupees

Naveen gave 15,000 rupees to other friend for two years at 12% per annum,then

S.I of 15000 rupees in two years = (15000×2×12) ÷ 100 = 3600 rupees

therefore total S.I = 2000+3600 = 5600 rupees

__This is your answer on S.I__

If we will have to find compound interest in two year of this amount,then we have to find S.I of two years for both friends on their rates.

Because their principal amount (P)for last one year will become = (main amount) + (S.I of first year)

so,, S.I of last year for friend (A) = (P×T×R) ÷ 100

S.I = (main amount ,which given to friend(A) +S.I of A in first year )×(1 year)×(the rate at which amount was given to A) ÷ (100)

S.I of last year for friend A = {( 10000+(10000×1×10 ÷ 100)}.×(1)×(10) ÷100

= (10000+1000)×(1)×(10) ÷ 100

= 11000×1×10 ÷ 100

S.I of last year for friend A = 1100

therefore C .I of two year for friend A = sum of S.I of both years = 1000+ 1100 = 2100 rupees

Now similar for other friend(B) bt this time rate will be 12% per annum and amount is 15000 rupees

S.I of 1st year = 15000×1×12÷100 = 1800 rupees

now principal amount for last year will become 15000 + 1800 = 16800 rupees

S.I of last year for B = 16800×1×12÷100 = 2016 rupees

Therefore C.I of two year for friend B = sum of S.I of both annum

=1800+2016 = 3816 rupees

Finally total compound interest (C.I) = C.I of two year for one friend(A) + C.I of two years for other friend (B)

total C.I = 2100 + 3816 = 5916 rupees

__This is your answer on C.I__