The expected answers were:

Gradient = Wp
                 VpIp

= 24.7 – 10
75.2 – 30.05

= 0.33

(k) The gradient of the curve and the Wp values from the table are the same,
                                                                    VpIp
(l) The current in the primary when the transformer is supplying current to load is higher. The total current in primary is the phasor sum of no-load current and current in primary when the transformer is supplying current to load.
The entries in the graph depended on the readings obtained. The wrong readings got by the candidates led to their wrong graphs.
It behoves the candidates to understand how to obtain accurate readings from instruments and this will go a long way in improving their performances.