Answers:
1. X= 0
2. X= 0
3. X=3
You can use this method to solve them step by step, hope it will help!
Answer:
30units,2900
Step-by-step explanation:
Given that Country Motorbikes Incorporated finds that it costs $400 to produce each motorbike, and that fixed costs are $1600 per day.
The price function is p(x) = 700 − 5x, where p is the price (in dollars) at which exactly x motorbikes will be sold.
If x units are produced and sold we have
Costs for x units = variable costs *x +Fixed costs 
Sales revenue = no of units sold * price = 
Profit funciton = P(x) = Sales revenue - Total cost
= 
To get maximum profit we use derivative test I derivative =0 and II derivative =negative

Producing 30 units will maximize the profit.
Max profit
=P(30) = 2900
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