Упрости выражения

1. \(\cfrac{42xy}{19z^6} ~ \cdotp \cfrac{57yz^4}{35x^5} = \) [ ];

2. \(18a^{10} \cdotp \cfrac{b^3}{9a^5}\) \(=\) [ ];

3. \(\cfrac{5ab^2}{13cd^2} ~ \cdotp 26c^2d \) \(=\) [ ];

4. \(\cfrac{a^2b^3}{13m^4n^8} ~ \cdotp (-\cfrac{65m^4n^7}{2ab^3})\) \(=\) [ ].