Serpent Tech Incorporation (SPI) issues a two-stage-coupon perpetual bond with the total par value of $1 billion. The coupon rate(paid quarterly with the first coupon payment happening three months from now- the last coupon payment for each year is also included in the income statement used for annual tax calculation purpose) set for the first ten years is 4 percent. After that, the coupon rate will jump to8% The YTM of this bond is10%. Assume28 percent marginal corporate tax rate.

Calculate the present value of interest tax shield to SPI based on this bond.