(6 Çarin has made a vase in clay that she will burn in an oven. The oven is heated with the vase in. When heating, the temperature is raised slowly. To control the oven, Carin measures the temperature at some times. In the diagram below you can see how the oven temperature is ° C at the beginning of the heating depends on the time x hours after the oven is switched on.
Carin assumes that the relationship between temperature and time is linear until the temperature is 450 ° C. At this temperature, the so-called peephole holes in the oven are clogged.
a) Determine the linear relationship.
b) How long from start does it take before the temperature is 450 ° C?
