Neco 2023 Agricultural Science Question 21

In a 2 ha cassava field, the initial proportion of plants infected with mosaic virus is 5\%. The disease spreads each week according to the logistic‑type rule: the proportion of newly infected plants equals \(0.3\)\times I_t\times \(1 - I_t\), where I_t is the proportion infected at the start of the week. After the first two weeks the farmer applies a foliar spray that reduces the infection‑rate constant from \(0.3\) to \(0.18\). After week 3 he replaces 40\% of the remaining susceptible plants with a resistant variety that is completely immune. Assuming the spray remains effective, what is the proportion of infected plants at the end of week 4? Express your answer as a percentage to one decimal place.