We present observations and analysis of an RS CVn-type double-lined eclipsing binary system , RU Cnc .
The system has been observed for over a century .
The high-quality long-cadence Kepler K2 C5 and C18 , newly obtained observations , and two radial velocity curves were combined and analyzed simultaneously assuming multi-spot model .
The masses , radii and luminosities of the component stars are precisely obtained as M _ { \textrm { c } } = 1.386 \pm 0.044 M _ { { } _ { \odot } } , M _ { \textrm { h } } = 1.437 \pm 0.046 M { { } _ { \odot } } , R _ { \textrm { h } } = 2.39 \pm 0.07 R { { } _ { \odot } } , R _ { \textrm { c } } = 5.02 \pm 0.08 R { { } _ { \odot } } , L _ { \textrm { h } } = 11.4 \pm 1.2 L { { } _ { \odot } } , L _ { \textrm { c } } = 12.0 \pm 1.0 L { { } _ { \odot } } and with a separation of \textrm { a } = 27.914 \pm 0.016 R { { } _ { \odot } } .
The distance of the system is determined to be 380 \pm 57 pc which is consistent with the Gaia DR2 result .
Long-term detailed period variation analysis of the system indicate a period decrease of 7.9 \times 10 ^ { -7 } days per year .
The results suggest the cooler component to be on the red giant branch ( RGB ) and the hotter one to be still on the main sequence .