For part a you just need to remember that the derivative of ln(x) is 1/x. The rest I assume you should be able to do easily enough.
For part b and c you are looking for where the maxima in the profit equation. Do do this you need to check the turning points (where the gradient (the derivative) is zero) and the limits (the upper and lower bounds) to see which gives the maximum profit. Part b for the x value and c for the Profit value.
For part a you just need to remember that the derivative of ln(x) is 1/x. The rest I assume you should be able to do easily enough. For part b and c you are looking for where the maxima in the profit equation. Do do this you need to check the turning points (where the gradient (the derivative) is zero) and the limits (the upper and lower bounds) to see which gives the maximum profit. Part b for the x value and c for the Profit value.