Conditions concurrent are those which are mutually dependent and are to be performed at the same time.
§ 28-1-404, MCA
En. Sec. 1953, Civ. C. 1895; re-en. Sec. 4901, Rev. C. 1907; re-en. Sec. 7403, R.C.M. 1921; Cal. Civ. C. Sec. 1437; Field Civ. C. Sec. 679; re-en. Sec. 7403, R.C.M. 1935; R.C.M. 1947, 58-207.