(i) The tree diagram is structured as follows:

• First branch: Toast (T) with probability 0.85, Bread roll (B) with probability 0.15.
• Second branch from Toast: Jam (J) with probability 0.8, No Jam (NJ) with probability 0.2.
• Second branch from Bread roll: Jam (J) with probability 0.4, No Jam (NJ) with probability 0.6.

(ii) To find the probability that Maria had toast given she did not have jam, use Bayes' theorem:

\(P(T \mid NJ) = \frac{P(T \text{ and } NJ)}{P(NJ)}\)

Calculate \(P(T \text{ and } NJ)\):

\(P(T \text{ and } NJ) = 0.85 \times 0.2 = 0.17\)

Calculate \(P(NJ)\):

\(P(NJ) = P(T \text{ and } NJ) + P(B \text{ and } NJ) = 0.85 \times 0.2 + 0.15 \times 0.6 = 0.17 + 0.09 = 0.26\)

Substitute back into Bayes' theorem:

\(P(T \mid NJ) = \frac{0.17}{0.26} = \frac{17}{26} \approx 0.654\)