Can someone please help me with this question?

3. In British Columbia, lakes with alkalinity values of less than 10. mg CaCo3 L are classified as being highly sensitive to acidification. A water sample from a Vancouver Island Lake has a pH of 7.18 and a 75.00 mL aliquot of the water requires 3.85 mL of 0.02034 mol L 1 to titrate it to the methyl orange end point (pH = 4.3): (a) [5 marks] Determine the total alkalinity of the sample, in units of mol * accept l'and mg CaCo3 Land state whether or not the lake is highly sensitive to acidification. (b) [6 marks] In another water sample the pH was measured to be 8.85 and the carbonate (CO32- ) concentration determined to be 6.5 x 10 mol/L. Calculate the concentrations of OH and HCO3 and then the total alkalinity (in units of mol H+ accept L-1)