Value the variance swap in Example 26.4 of Section 26.16 assuming that the implied volatilities for options with strike prices $800,850,900,950,1,000,1,050,1,100,1,150$, 1,200 are $20 \%, 20.5 \%, 21 \%, 21.5 \%, 22 \%, 22.5 \%, 23 \%, 23.5 \%, 24 \%$, respectively.