Ark Invest, founded by money manager Cathie Wood, added more units of its own spot Bitcoin (CRYPTO: BTC) exchange-traded fund on Friday, taking the week’s accumulation to $44 million. What Happened: Ark bought 316,526 units of ARK 21Shares Bitcoin ETF (CBOE: ARKB) on Friday, and the value of the purchase based on the ETF’s closing price of $41.73 was $13.21 million. At the same time, Ark sold 510,337 units of ProShares Bitcoin Strategy ETF (NYSE:BITO) valued at $10.25 million. BITO seeks to generate returns corresponding to the performance of Bitcoin by investing in Bitcoin futures contracts. …