Japanese e-commerce giant Rakuten Inc. said Friday it will offer a monthly 20-gigabyte mobile data plan for 1,980 yen ($19) from April, the cheapest among major Japanese carriers, in a bid to attract subscribers amid intensifying price competition.The new service plan follows those announced by larger rivals NTT Docomo Inc. and SoftBank Corp. last month priced at 2,980 yen, including free unlimited calls of up to five minutes from March.KDDI Corp., the operator of "au" brand, said earlier in the month it would offer a plan for similar data usage without free voice calls for 2,480 yen.Rakute…READ FULL ARTICLE