Ford Motor Co. said on Tuesday its fourth-quarter results would include an $8.2 billion gain on its investment in Rivian Automotive Inc., following the electric-vehicle maker’s blockbuster market debut in November. Rivian had soared as much as 53 percent to cross $100 billion in the biggest initial public offering of 2021, but the company’s shares have dropped over 27 percent since then. The stock closed 8.5 percent lower on Tuesday after hitting its weakest since the IPO amid a broader tech selloff on Wall Street. Ford, an early investor in Rivian, currently owns about 12 percent of the California-based company and has itself been racing toward electrification in a shift away from traditional gasoline-powered cars as demand for green transport surges. It has pledged to invest more than $30 billion on EVs by 2030. In 2019, the 118-year-old Detroit automaker invested $500 million in Rivian, with plans to use the …