Consider the following statements:
P. Walls of one brick thick are measured in square meters.
Q. Walls of one brick thick are measured in cubic meters.
R. No deduction in the brickwork quantity is made for openings in walls up to 0.1 $$m^2$$ area.
S. For the measurement of excavation from the borrow pit in a fairly uniform ground, dead men are left at suitable intervals.
For the above statements, the correct option is

Given that the scope of the construction work is well-defined with all its drawings, specifications, quantities and estimates, which one of the following types of contract would be most preferred?

Let $$\,\,W = f\left( {x,y} \right),\,\,$$ where $$x$$ and $$y$$ are functions of $$t.$$ Then, according to the chain rule, $${{dw} \over {dt}}$$ is equal to

A two-faced fair coin has its faces designated as head $$(H)$$ and tail $$(T)$$. This coin is tossed three times in succession to record the following outcomes: $$H, H,H.$$ If the coin is tossed one more time, the probability (up to one decimal place ) of obtaining $$H$$ again, given the previous realizations of $$H, H$$ and $$H$$, would be _____.