(a) Joint account.--A joint account belongs, during the lifetime of all parties, to the parties in proportion to the net contributions by each to the sum on deposit, unless there is clear and convincing evidence of a different intent.

(b) Trust account.--Unless a contrary intent is manifested by the terms of the account or the deposit agreement or there is other clear and convincing evidence of an irrevocable trust, a trust account belongs beneficially to the trustee during his lifetime, and if two or more parties are named as trustees of the account during their lifetimes beneficial rights as between them are governed by subsection (a). If there is an irrevocable trust, the account belongs beneficially to the beneficiary.