Given stage delays: $T_1=800$, $T_2=500$, $T_3=400$, $T_4=300$ ps. Pipeline clock $T_{clk}= \max(T_i)$ (+ latch overhead ignored).

Before modification:
$$T_{clk1}= \max(800,500,400,300)=800\text{ ps}$$
Throughput $= 1/T_{clk1}$ instructions per ps.
$$f_1 = \frac{1}{800\text{ ps}} =1.25\times10^{9}\text{ instr/s}$$

After splitting first stage into $600$ ps + $350$ ps, stages become: $600,350,500,400,300$.

$$T_{clk2}= \max(600,350,500,400,300)=600\text{ ps}$$
$$f_2 = \frac{1}{600\text{ ps}} =1.667\times10^{9}\text{ instr/s}$$

Throughput increase:
$$\%\Delta = \frac{f_2-f_1}{f_1}\times100 = \frac{\frac{1}{600}-\frac{1}{800}}{\frac{1}{800}}\times100 = \left(\frac{800}{600}-1\right)\times100$$
$$= \left(1.333...-1\right)\times100 = 33.33\%$$

Speedup $= 800/600 = 1.33$.

If latch overhead $t_l$ (e.g., 20ps) included, then $T_{clk1}=800+t_l$, $T_{clk2}=600+t_l$, increase $= \frac{800+t_l}{600+t_l}-1 \approx 32.25\%$ for $t_l=20$ps. Ideal approx 33.33% increase.

Note: Total latency increases slightly ($2000$ ps → $2150$ ps) but steady-state throughput improves due to smaller max stage delay (pipeline bottleneck reduced).