We need to solve: `2000 − t^2− 140t > 500`.

`1500 − t^2− 140t > 0`

`t^2+ 140t − 1500 < 0`

`(t + 150)(t − 10) < 0`

So ` −150 < t < 10`.

But t cannot be negative, so `0 ≤ t < 10`.

The solution graph is:

246810120-2tOpen image in a new page

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