Exercise in mixture calculation?

Hey, I urgently need help with the following question!!

You mix 300 ml of 0.40 molar sulfuric acid with 500 ml of 2 molar sulfuric acid. This yields 1036 g of a mixture with a density of 1.07 kg/dm3.

a) Calculate the mass fraction of sulfuric acid in the resulting solution!

b) How many grams of water must be removed to obtain an 18% sulfuric acid solution?

[M(H2SO4)=98.0g/mol]

Thank you in advance!