Analisis pengaruh dana pihak ketiga (DPK), loan deposit ratio (LDR), non performing loan (NPL), biaya operasional pendapatan operasional (BOPO) dan suku bunga sertifikat Bank Indonesia (SBI) tehadap return on asset (ROA) : studi kasus PT. Bank Persero, tbk 2009-2014 - Sandhi Guntoro