If \[\mathbf{7a}\text{ }+\text{ }\mathbf{3b}\text{ }:\text{ }\mathbf{4a}\text{ }+\text{ }\mathbf{9b}\text{ }=\text{ }\mathbf{9}\text{ }:\text{ }\mathbf{7}\] then the value of \[\frac{\mathbf{a+b}}{\mathbf{a}}\] is _______.

• A. \[\frac{53}{60}\]
• B. \[\frac{73}{70}\]
• C. \[\frac{73}{60}\] 
• D. \[\frac{53}{70}\]
• E. None of these