Word Problem Please need help on how to solve this asap

Question

A manufacturer sells a product for $18 per unit, selling all that is produced. Total costs are made up of fixed costs of $1100 and variable costs of $2.50 per unit.

1. Find an expression for profit (𝜋).
2. Find the break-even level of production (to the nearest unit).
3. Find the break-even level of production if variable costs increase by 20%.
4. Suppose the manufacturer can only sell at a price of $18 per unit when selling less than 500 units. For quantities above 500 units the price drops to $15 per unit. Write out a split revenue function (𝑟) that reflects this.

Another question

A university subject has three items of assessment – a quiz, an assignment and an exam. Suppose a student scored 4.5/10 on the quiz worth 25% and 72/90 on the assignment worth 35%. The remaining 40% weighting is for the exam. If this student would like to achieve a distinction (or 75%) mark overall in their subject, what mark do they require on their exam?

Answer 1

Profit = pi = 18x - 2.5x -1100

pi = 15.5x -1100

breakeven is when pi=0 = 15.5x -1100

x = 1100/15.5 = about 71

2.5(1.2)=3

pi=15x-1100

x = 1100/15 =73 1/3 to break even

45(.25) + 80(.35) + x(.4) = 75

x= (75-28-11.25)/.4= 35.75/.4= 89.375 needed to get 75

4.5/10=45/100=45%

72/90=80/100=80%

get the weighted average =75/100=.75= 75%