If you don't mind explaining your process for these? I'm quite stuck on the way to answer. Thank you!

7. Joshua's preferences over cookies (C) and donuts (D) are represented by the utility function U(C, D) = C' + D', MUc = 20, MUD = 2D If the price of a cookies is $1 and the price of a donuts is $2, and Joshua can spend a combined total of $10 on these goods, find Joshua's optimal consumption bundle. (a) C =4, D=2 (b) C =5, D=0 (c) C =0, D = 10 (d) C =5, D = 10 (e) None of the above.8. Bob's preferences for water (w) and coke (c) can be described by utility function U(w, c) = In(w) +c, MUw - -, MU. =1. If the price of a water is $1 and the price of a coke is $2, and Bob has $4, find Bob's optimal consumption bundle. (a) w = 2, c=1 (b) w =4, c=0 (c) w =0, c=2 (d) w =4, c= 2 (e) None of the above.9. Bob's preferences for water (w) and coke (c) can be described by utility function U(w, c) = In(w) +c, MU. = 1, MU. =1. But now the price of Coke suddenly increased to $8 per can. If the price of a water is $1 and the price of a coke is $8, and Bob has $4, find Bob's optimal consumption bundle. (a) w=8, c= - (b) w =4, c= 0 (c) w =0, c= 2 (d) w =4, c= 2 (e) None of the above.2. Andrew's preferences for doing research and sleeping is U(x, y) =6 . VS + R, MUs = #, MUR = 1, where R is number of hours spent on research and S is number of hours spent on sleep. Opportunity cost of sleeping and doing research is the same and equal 1 hour (ps = PR = 1). What's Andrew's optimal schedule if there is only 24 hours in a day (I = 24) (a) S=0, R=0 (b) S =9, R = 15 (c) S = 24, R=0 (d) S =6, R=18 (e) None of the above