Using the model, write down a second equation in $a$ and $b$ .

Using your graphic display calculator or otherwise, find the value of $a$ and of $b$ .

Use the model to predict the temperature of the liquid $60{\text{ seconds}}$ after the start of heating.

$50a + b = 37$ (A1)(A1)     (C2)

Note: Award (A1) for $50a + b$ , (A1) for $= 37$ .

$a = 0.4$, $b = 17$     (A1)(ft)(A1)(ft)     (C2)

Notes: Award (M1) for attempt to solve their equations if this is done analytically. If the GDC is used, award (ft) even if no working seen.

$T = 0.4(60) + 17$     (M1)

Note: Award (M1) for correct substitution of their values and $60$ into equation for $T$.

$T = 41{\text{ }}{{\text{(}}^ \circ }{\text{C}})$     (A1)(ft)     (C2)

Note: Follow through from their part (b).