The function would be h = 270 - 2.5s, where h is the height (in feet) and s it the time (in seconds) that has passed.
The 270 represents the initial value, which is given. We are told that the initial height of the block is 270 feet.
2.5s represents the feet that it has descended. We know the block is lowered at a rate of 2.5 feet per second. Multiplying this by s, the time, will give us how much it has descended.
It says "Relief washed over us. Whatever had been chasing us was long gone. We were home and finally safe behind a locked door." She's /he's telling the emotions.