# Calculate NaOH concentration

Having trouble with these...

How do you calculate the NaOH concentration (MW=40.00) of a solution that has 4g of solid NaOH dissolved in 200 mL of water?

and then to prepare the primary standard, how do you calculate the expected mass of benzoic acid required to react in stoichiometric proportion with 20 mL of the NaOH solution (MW = 122.12)?