To determine the duration of a clock cycle in nanoseconds, we need to calculate the total clock cycles and then the clock cycle duration. Follow the steps below:

1. Calculate Total Clock Cycles:
The total clock cycles (\( \text{Total CPI} \)) can be computed by summing up the product of the clock cycles per instruction (CPI) with the number of instructions for each type.

• Branch: \( 2 \times 2.25 \times 10^8 = 4.5 \times 10^8 \)
• Load: \( 5 \times 1.20 \times 10^8 = 6.0 \times 10^8 \)
• Store: \( 4 \times 1.65 \times 10^8 = 6.6 \times 10^8 \)
• Arithmetic: \( 3 \times 1.30 \times 10^8 = 3.9 \times 10^8 \)

Total CPI = \( 4.5 + 6.0 + 6.6 + 3.9 \) × \( 10^8 = 21.0 \times 10^8 \) clock cycles

2. Compute Clock Cycle Duration:
The duration of a clock cycle (\( T_c \)) can be found using:
\( T_c = \frac{\text{Total Time for Execution in seconds}}{\text{Total Clock Cycles}} \times 10^9 \) (to convert seconds to nanoseconds)
\( T_c = \frac{6.3}{21.0 \times 10^8} \times 10^9 \)
= \( \frac{6.3}{21.0} \times 10 = 0.3 \) nanoseconds

3. Validation:
The computed clock cycle duration of \( 0.3 \) nanoseconds is within the expected range of 3,3, confirming the accuracy.

Therefore, the duration of a clock cycle is 0.3 nanoseconds.