1. **Problem Statement:** We are given two points representing depth and pressure: (4, 140) and (10, 200). We need to find the linear equation relating pressure $P$ to depth $d$, and answer related questions. 2. **Formula and Rules:** The equation of a line is $P = md + b$, where $m$ is the slope and $b$ is the pressure intercept (pressure at depth 0). 3. **Calculate the slope $m$:** $$m = \frac{P_2 - P_1}{d_2 - d_1} = \frac{200 - 140}{10 - 4} = \frac{60}{6} = 10$$ 4. **Find the intercept $b$:** Using point (4, 140): $$140 = 10 \times 4 + b \implies b = 140 - 40 = 100$$ 5. **Equation of the line:** $$P = 10d + 100$$ 6. **Interpret $b$ (pressure intercept):** The intercept $b = 100$ kPa represents the pressure at the surface (depth 0 metres). 7. **Find depth when pressure is 245 kPa:** $$245 = 10d + 100 \implies 10d = 145 \implies d = 14.5$$ metres 8. **Find pressure at depth 17 metres:** $$P = 10 \times 17 + 100 = 170 + 100 = 270$$ kPa 9. **Interpret slope $m$:** The slope $m = 10$ kPa/m means pressure increases by 10 kPa for every 1 metre increase in depth. **Final answers:** - Equation: $P = 10d + 100$ - Pressure intercept: 100 kPa (pressure at surface) - Depth at 245 kPa: 14.5 metres - Pressure at 17 metres: 270 kPa - Slope: 10 kPa/m (rate of pressure increase with depth)