The total asset value ($V_0$) of the bank is the sum of its liabilities and equity: 29.0 + 17.0 + 20.0 + 13.0 = $79.0 billion. To find the required debt level ($K$) that results in a 1% probability of default (a 99.0% confidence level for economic capital), we use the distance to default (DD) formula:

$DD = \frac{\ln(V_0/K) + (\mu - \sigma^2/2)T}{\sigma \sqrt{T}}$

For a 99.0% confidence level (1-tailed normal distribution), the critical value $d_2$ (or DD) is approximately 2.33.

Plugging in the values: $\frac{\ln(79.0/K) + 0.150 - 0.280^2/2}{0.28} = 2.33$

Solving for $K$ gives K \approx \`46.0$ billion. The Economic Capital (EC) is the difference between the current total asset value and this threshold $K$: $EC = V_0 - K = 79.0 - 46.0 = \$33.0`$ billion.

This matches option B perfectly.