付款条件的英文表达 — 国际贸易计算题

某出口公司与日本客户成交一批自行车零件，合同金额为 USD 58,000.00。合同付款条款英文表述如下："Payment: 30% of the contract value shall be paid by T/T in advance after signing the contract, and the remaining 70% shall be paid by L/C at sight before shipment." 请根据该付款条款，计算：（1）买方签约后应电汇的预付款金额；（2）买方开立即期信用证的金额。