Answer:
(a) the price per units is $5.0
(b)the number of units demanded = 7
Step-by-step explanation:
The demand function is given by 
(a) Now, we have to find the value of p when q = 6
Substitute q = 6 in the above equation

On simplifying, we get

Rounding to nearest cents, we have

Therefore, the price per units is $5.0
(b)
Now, we have to find q for p = $2.99

Divide both sides by 100

Take natural log both sides

On simplifying, we get

Therefore, the number of units demanded = 7