The weights of female 18-year-old students can be modeled using a normal distribution. This is a common assumption for biological measurements, which tend to be symmetrically distributed around a mean.

For the normal distribution, we need to specify the mean and the variance. According to the mark scheme, a suitable mean is 60 kg, and a suitable variance is 90 kg².

These values are within the sensible range provided: mean between 40 kg and 80 kg, and variance between 16 kg² and 225 kg².