The efficiency of two home heating systems are being compared.

The two systems are being measured on how quick it takes to warm a room when put on full from a temperature of 4°C.

Heat – Ex guarantees to get to 20°C in under 15 minutes.

Warmo guarantees to beat any of the competition to 20°C.

Both sets of results are shown on the graph.

Which guarantees are correct?

Both companies’ guarantees are correct.

Only Warmo company guarantee is correct.

It is not possible to tell from the graph

Only Heat-Ex company guarantee is correct.

Neither company guarantee is correct.